Power surges caused by lightning and/or signal transients occurring on the electric distribution grid can cause an outdoor luminaire to remain turned on indefinitely. Specifically, after experiencing a surge, the luminaire can remain on during the day, when it would otherwise be automatically turned off. This type of failure is known as a “day burner” failure, and it can typically be pinpointed to the failure of one or more relays included in the luminaire.
A relay can fail because the high current densities resulting from a surge can lead to an above-rated power dissipation at the relay's contacts, causing them to melt and weld together. As such, the relay remains in the closed position indefinitely, and the luminaire thus remains on. Furthermore, the relay cannot be actuated in its open position in order to cut-off power delivery to the luminaire, because the relay's contacts are physically welded together.
This type of failure can cause an energy company to erroneously bill their customers (e.g. municipalities) for faulty light fixtures that are on all the time. Moreover, there can be high costs for the original equipment manufacturer (OEM) to service these parts once they are returned by the customer.
While relays having power dissipation, voltage, and current ratings higher than those of commonly used electro-mechanical relays can be employed to circumvent day burner failures, high-end relays can increase the overall cost of luminaires as well as the complexity of the control circuitry needed to operate the relays. As such, there is a need for devices and methods that can prevent day burner failures of luminaires without increasing cost or circuit complexity.